This invention relates to an antenna connecting apparatus useful in the automotive industry. More specifically, this invention relates to connecting an on-glass antenna to a transmission cable useful in automotive audio and communication devices.
One difficulty in utilizing on-glass antennae is obtaining a convenient method for connecting a printed on-glass metallic pattern to a transmission cable while providing wide band impedance matching. The impedance matching must be done in the FM frequency band, where the coaxial cable impedance is often 50 ohms, and the much lower AM frequency band, where the antenna and the receiver input impedance is closer to 6,000 ohms.
The present invention is based on a transformer design. The purpose of the transformer is to obtain the proper impedance matching at the FM frequency band from 88 to 108 MHz. A capacitor may also be used if the printed grounding pattern does not contain the proper capacitance. This capacitor behaves like a short circuit in the FM frequency band, and an open circuit in the AM frequency band. The combination results in a wide bandwidth and a transformation from the coaxial cable impedance to the antenna impedance. A convenient method of attachment is also provided for in the current invention.
Although described with respect to the fields of automotive audio and communication devices, it will be appreciated that similar advantages of a convenient wide band antenna connector may obtain in other applications of the present invention. Such advantages may become apparent to one of ordinary skill in the art in light of the present disclosure or through practice of the invention.